Cyanohydrin compounds are useful as starting materials for synthesis of various compounds, e.g., for production of α-hydroxyester compounds. As such a process for producing a cyanohydrin compound, a process for achieving a synthesis by cooling and stirring a carbonyl compound including a catalyst and serving as a raw material, supplying hydrogen cyanide slowly thereinto, proceeding with a reaction while removing reaction heat successively (hereinafter referred to as “batch process”) is commonly used. The reaction between the carbonyl compound and the hydrogen cyanide is very high in speed and also high in reaction heat. Therefore, the hydrogen cyanide is supplied over a long period of time so that the reaction system is inhibited from abruptly rising in temperature.
Besides the batch process, there have been known processes described in Patent Literatures 1 to 7 for producing cyanohydrin compounds.
For example, Patent Literatures 1 and 2 disclose processes for continuously producing cyanohydrin with use of hydrogen cyanide gas. Patent Literatures 3 and 6 disclose processes for producing acetone cyanohydrin, including continuously supplying hydrogen cyanide into a reaction tower and discharging it out of the reaction tower. Patent Literature 4 describes a process for producing acetone cyanohydrin, including continuously introducing acetone and hydrogen cyanide into a reactor vessel and producing acetone cyanohydrin by use of a difference in specific gravity between the starting materials and the product. Patent Literature 5 describes a process for performing a continuous reaction by causing an anion-exchange resin to exist in a flowing state in a mixed solution of acetone and hydrogen cyanide or a mixed solution of a product of acetone and hydrogen cyanide. Patent Literature 6 discloses a process for producing cyanohydrin, including continuously supplying hydrogen cyanide and an aliphatic carbonyl compound into a reaction tower and discharging them out of the reaction tower. Patent Literature 7 discloses a process for producing acetone cyanohydrin by reacting acetone with hydrogen cyanide in the presence of a basic catalyst in a reactor vessel.